This is the legacy method to mark root certificates as usable for qualified certificates. Qualified certificates are capable of creating legally binding signatures in the same way as handwritten signatures. The modern method to mark such root certificates is to use the "qual" flag in the system trustlist.txt; see the gpg-agent man page for details.
Comments int his file start with a hash mark and empty lines are ignored. Lines do have a length limit but this is not a serious limitation as the format of the entries is fixed and checked by gpgsm: A non-comment line starts with optional whitespace, followed by exactly 40 hex characters, white space and a lowercased 2 letter country code. Additional data delimited with by a white space is current ignored but might late be used for other purposes.
Note that even if a certificate is listed in this file, this does not mean that the certificate is trusted; in general the certificates listed in this file need to be listed also in ‘trustlist.txt’. This is a global file an installed in the sysconf directory (e.g. ‘/etc/gnupg/qualified.txt’).
Every time gpgsm uses a certificate for signing or verification this file will be consulted to check whether the certificate under question has ultimately been issued by one of these CAs. If this is the case the user will be informed that the verified signature represents a legally binding (``qualified'') signature. When creating a signature using such a certificate an extra prompt will be issued to let the user confirm that such a legally binding signature shall really be created.
Because this software has not yet been approved for use with such certificates, appropriate notices will be shown to indicate this fact.